fix(libso): include headers from RTL simulators

Since libso requires some headers from RTL simulators, this commit
adds the corresponding include flags. As we are not sure whether
the headers are simulator-dependent, we include VCS headers with a
higher priority than Verilator.

We also add a CI test for difftest-so on XiangShan

.github/workflows/main.yml

@@ -306,3 +306,34 @@ jobs:
             make simv VCS=verilator -j2
             ./build/simv +workload=$WORKLOAD +b=0 +e=-1 +diff=$REF_SO +max-instrs=5000 +warmup_instr=1000
             make clean
+
+  test-difftest-xiangshan:
+    # ubuntu 22.04 has the same version of libc as our VCS machines
+    runs-on: ubuntu-22.04
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Prepare environment
+        run: |
+            cd $GITHUB_WORKSPACE/..
+            wget https://github.com/OpenXiangShan/xs-env/raw/refs/heads/master/install-verilator.sh
+            wget https://github.com/OpenXiangShan/xs-env/raw/refs/heads/master/setup-tools.sh
+            sudo bash setup-tools.sh
+
+      - name: Prepare XiangShan
+        run: |
+            cd $GITHUB_WORKSPACE/..
+            git clone --depth 1 https://github.com/OpenXiangShan/XiangShan.git
+            cd XiangShan && make init && rm -rf difftest && cp -r $GITHUB_WORKSPACE .
+            echo "NOOP_HOME=$(pwd)" >> $GITHUB_ENV
+
+      - name: Chisel Elaboration
+        run: |
+          cd $NOOP_HOME
+          make sim-verilog CHISEL_TARGET=chirrtl JVM_XMX=10G
+
+      - name: Build difftest-so
+        run: |
+          cd $NOOP_HOME
+          make -C difftest difftest-so

libso.mk

@@ -10,10 +10,26 @@ ifeq ($(WITH_DRAMSIM3),1)
 LD_LIB  	 = -L $(DRAMSIM3_HOME)/ -ldramsim3 -Wl,-rpath-link=$(DRAMSIM3_HOME)/libdramsim3.so
 endif
 
+# Include headers that are implicitly included by RTL simulators
+# Priority: (1) VCS, (2) Verilator
+ifneq ($(VCS_HOME),)
+LIB_CXXFLAGS += -I$(VCS_HOME)/include
+else
+VERILATOR_ROOT = $(shell verilator -V 2>/dev/null | awk '/VERILATOR_ROOT/ {print $$3; exit}')
+ifneq ($(VERILATOR_ROOT),)
+LIB_CXXFLAGS += -I$(VERILATOR_ROOT)/include/vltstd
+else
+LIBSO_WARNING_MISSING_HEADERS = 1
+endif
+endif
+
 $(CC_OBJ_DIR):
 	mkdir -p $(CC_OBJ_DIR)
 
 difftest-so: $(CC_OBJ_DIR)
+ifeq ($(LIBSO_WARNING_MISSING_HEADERS),1)
+	@echo "No available RTL simulators. Headers may be missing. Still try to build it."
+endif
 	cd $(CC_OBJ_DIR) 					&& \
 	$(CC) $(LIB_CXXFLAGS) $(LIB_CXXFILES)			&& \
 	$(CC) -o $(LIBDIFFTEST_SO) -m64 -shared *.o $(LD_LIB)